[1. Complete "back-out" of all installed custom software] + 2. factory reset [+ 3. firmware downgrade]. Step 1 optional, not necessary if firmware is downgraded properly. Step 3, "nuke it from orbit, only way to be sure option" is best. But non-optional step 2, factory reset, that's a showstopper. I can't (for political reasons, meaning I share this Kindle with other people) clear all content.